1. Field of the Invention
This invention relates generally to fluid control devices, and, more particularly to an improved fluid flow fuse for stopping the flow of water in a system when the water flow rate through the fuse exceeds a predetermined amount.
2. Description of Related Art
Many fluid systems, such as water sprinkler systems used on lawns, at golf courses, on freeway embankments, in housing tract common areas, in gardens, etc., are typically laid out with groups of sprinkler heads, which are controlled by one or more shutoff valves. The shutoff valves may be manual, but, in larger systems, are usually electrically operated, such as solenoid operated valves. In presently known systems, when a sprinkler head breaks or the line feeding the sprinkler heads breaks, a large flow of water results and continues until the shutoff valve for the line having the break, is closed. Many attempts have been made to solve the problems that occur when such breakage occurs to, among other things, prevent wasting water.
Known prior art devices are shown in U.S. Pat. No. 5,105,850 to Harris and U.S. Pat. No. 5,722,454 to Smith et al., which disclose valve housings having an inlet and an outlet and a valve assembly mounted in the housing to control fluid flow between the inlet and the outlet. Valve seats are mounted in the housings, and valve stem guides having a plurality of passages permitting fluid flow therethrough are also mounted in the housings. Harris includes an adjustable bolt having a hollow bolt shaft extending into the housing and the valve stem extends into the hollow bolt so as to guide the valve stem. A stop is mounted on the valve stem to limit motion of the valve stem and a spring is retained between the end of the adjusting bolt and the stop to bias the plunger away from the valve seat. The spring is arranged such that a predetermined fluid flow rate produces a force on the plunger sufficient to move it into contact with the valve seat and shut off the fluid flow. While Smith et al. includes a diaphragm wherein at least one spring and the pressure differential on each side of the diaphragm controls fluid flow through the fuse. While the devices set forth in these patents solve a number of problems, they are not optimized with respect to operating force margin, cost effectiveness, and field repair. Furthermore, the known fuses are susceptible to contaminants, friction and manufacturing tolerances.
A number of other prior art devices are known which act solely as pressure regulators of various forms and functions, while some known prior art devices control the flow of the fluid through the device. One such fluid flow device is shown in U.S. Pat. No. 4,250,915 to Rikuta, which discloses an automatic fluid control valve for maintaining a substantially constant fluid rate. This device includes a partition wall within a valve casing between a fluid inlet and a fluid outlet. A restriction-adjusting member is mounted movably in the valve casing, and includes a tapered end movable relative to a valve port in the partition wall to define a restricted passageway for fluids, with the adjacent walls of the valve port. A valve stem is movable within the casing, and has a valve thereon cooperable with the valve port to regulate the flow of fluid therethrough in response to changes in fluid pressure differential. A diaphragm is operably connected to the valve stem, and separates a region within the valve casing into a pair of pressure-differential chambers, and a fluid passage is formed in the casing communicating one pressure-differential chamber with the inlet chamber, while the other pressure-differential chamber communicates with the downstream side of the valve port. This valve, however, is always trying to maintain the same flow rate, and does not shut off flow of fluid therethrough if the downstream pressure drops dramatically.
A further prior art device is disclosed in U.S. Pat. No. 942,112 to Sprecher, which discloses a gas pressure regulator having a poppet-type valve member or plug j attached to a diaphragm 1, with a biasing means s pressed against the valve plug 1, and a continuous, elongated, restricted orifice/pressure measuring passageway r through the plug j. Sprecher, however, is drawn to a gas pressure regulator, and not a valve that automatically slowly and smoothly shuts off an excessive rate of flow of water in a sprinkler system.
Therefore, there exists a need in the art for a "water flow fuse" to accurately sense the fact that an abnormally high flow of water exists, and to then shut off the flow of water through the valve, automatically, after a built-in, mandatory time delay, and which more accurately senses and utilizes downstream pressure. With the use of improved fluid flow fuses of the present invention, which do not operate so rapidly, water hammer is avoided. Furthermore, the improved device of the present invention more smoothly controls the stopping of the fluid flow through the fuse in a more efficient manner, including using the sensed pressure downstream to more accurately control closing of the device.